The field of this invention generally relates to pyrotechnic initiators, and more particularly to a pyrotechnic initiator adapted for use in a high-pressure environment.
Pyrotechnic initiators have many uses in industrial and consumer applications. For example, an initiator may be used as a component in a motor vehicle airbag inflator device. One known inflator device includes a pressure chamber having gas sealed within at high pressure, typically an inert gas at a pressure of 3000-4000 psi. The gas and heat released from initiator combustion causes a pressure spike within the sealed chamber, which is used to inflate the airbag. The pressure chamber and components exposed to the pressure within are constructed from materials and components that can contain and withstand that pressure over a period of years. Components of the inflator device that cannot withstand such high pressure are isolated from the pressure chamber by burst discs or other structural members. Known pyrotechnic initiators are not designed to withstand the high-pressure within the sealed gas unit, and must be isolated from it. Isolating components from the pressure chamber generally requires complex machine work and high strength materials, both of which are expensive. Typically, to isolate a pyrotechnic initiator from the pressure chamber, a thick metal cup surrounds a portion of the initiator and bears the loads generated by the high pressure within the pressure chamber. Because the pyrotechnic charge in the initiator must rupture or burst that thick cup in order to perform useful work, a more powerful pyrotechnic charge must be used than would be required in the absence of the cup. Although such a cup may be stamped from a thick metal sheet, a stamping operation utilizing thick metal is difficult and expensive.
A pyrotechnic initiator adapted for insertion into a sealed gas unit includes an igniter, over which a nonconductive body is molded. The nonconductive body resists the pressure inside a sealed gas unit and protects the igniter from that pressure. The body is molded onto a retainer, onto which a cup is attached to form a pressure seal and a hermetic seal against the gases within the sealed gas unit. The body is overmolded to carry substantially all of the structural loads exerted by the gas within the sealed gas unit on the initiator, allowing the cup to be made substantially thinner than previously possible.